Composite silica nanoparticle/polyelectrolyte microcapsules with reduced permeability and enhanced ultrasound sensitivity

Abstract

Many chemical and biomedical systems require delivery and controlled release of small molecules, which cannot be achieved by conventional polyelectrolyte-based layer-by-layer capsules. This work proposes an innovative hybrid microcapsule by incorporating in situ formed silica nanoparticles within or on the shell. The influence of various experimental conditions on the stability, mechanical strength and morphology of capsules w as investigated, and characterised by SEM, TEM, XRD, EDX and FTIR. The multifunctional capabilities of formed capsules were examined by encapsulating a small molecule Rhodamine B (Rh-B), which could be further released by an ultrasonic trigger. The results show that in situ formed SiO2 nanoparticles through hydrolysis greatly reduced the permeability of the shell yet with increased mechanical strength and ultrasound response. SiO 2 nanoparticles were shown to be distributed on the surface or inside polyelectrolyte shell, acting as supports for free -standing capsules in both liquid and dry environment. Rapid Rh-B molecules release and the fragmentation of the capsule shells were observed under 50W ultrasound irradiation for a few seconds. Such innovative capsules with capability of small molecule encapsulation and high ultrasound sensitivity could be promising for many applications where pulse release of small molecules is required.

Transport and Deposition of Carbon Nanoparticles in Saturated Porous Media

“…A simplified hydrothermal reaction is used to produce carbon nanoparticles [14,44]. First, 0.2 g of D-(+)-xylose (C5H10O5) was dissolved in 20 mL of DI-water; then, the solution was transferred into a Teflon-lined, stainless steel autoclave.…”

Bifunctional ultraviolet/ultrasound responsive composite TiO2/polyelectrolyte microcapsules

“…Compared with our silica/PE composite microcapsules, the external surface of the as-made TiO2/PE capsule was smoother. 5 This means the formed TiO 2 NPs were finer grained and homogeneously distributed on the polymer shells, arising from a relatively low nucleation and growth rate due to the low supersaturation of the precursor. Energy dispersive spectroscopy (EDX) analysis of the composite capsules indicated the presence of large amounts of C, O, and Ti and a tiny amount of S (see the inset in Figure 1c).…”

“…Positively charged PAH and negatively charged PSS were assembled alternately onto the freshly synthesised CaCO 3 cores. 5 After reaching a certain layer number, the templates were removed to obtain hollow PE capsules. Then, TiO 2 NPs were incorporated into the polymer shells through the in situ hydrolysis of TIBO under a well-controlled process.…”

“…12 Very recently, we developed a novel technology of in-situ production of nanoparticles in PE capsules. 5 Silica nanoparticles were successfully introduced into prefabricated LbL PE microcapsules by in situ hydrolysis of tetraethyl orthosilicate (TEOS), producing hybrid capsules with low shell permeability, high mechanical strength and strong ultrasound sensitivity. An example study, the encapsulation of a small molecule cargo (Rh-B) and controlled release through ultrasound treatment showed wide potential applications.…”

“…The introduction of inorganic nanoparticles can not only increase the shell mechanical strength and reduce their permeability, making them suitable for small molecules loading, but would also empower the capsules with new functionalities such as responsiveness to certain stimuli. 5 Various NPs have been incorporated into capsules with enhanced functions in recent years, which includes silica for ultrasound-triggered release, Fe3O4 for magnetically navigated drug delivery, and gold for visible and near-infrared (NIR) light responsive capsule systems. [6][7][8] Current design and synthesis of inorganic/organic composite capsules has been focused on assembling prefabricated inorganic NPs into soft polyelectrolyte (PE) shells.…”